Synchronizing system for television apparatus



June 28, 1932. c. w. JEFFRIES 1,355,190

I 'SYNCHRONIZING SYSTEM FOR TELEVISION APPARATUS Filed Oct. 23. 1929 2. SheetS-Sheet 1 INVENTOR ATTORNEY June 28, 1932. C JEFFRES 1,865,190

SYNCHRONIZING SYSTEM FOR TELEVISION APPARATUS Filed Oct. 25, 1929 2 sheets-sneer 2 AAAA n v ATTORNEY Patented June --2a, 1932 UNITED STATES PATENT o-Fncs 'CHABLE SW. JEI'I'BIES, OF LA CHARLES, LdUISIANA, ASSIGR'OB OF ONE-FOURTH TO MASON P. EBWIN, OF LAKE CHARLES, LOUISIANA t I BYWCHBONIZING sirs'rmr FOR TELEVISION APPARATUS Application filed October 28 1929 Serial N0. 401,779.

The invention relates to television apparatus and has articular reference to means for synchronizmg the speed of rotation of the scanning disc of a receiver with that of a transmitter. I

The principal object of the invention, generally speaking, is to provide in a television apparatus means whereby to obtain an absolute and perfect synchronization of the scanning disc of the receiver with respect to the rotation of the scanning disc of the transmitter, this being an essential feature in. the operation. 1

It is well known that in. television apparatus it is customaryto make use in the transmission system of 'a disc provided with a spirally arranged series of holes cooperating with or disposed between a source of light, properly shielded, and a photoelectrlc cell, and it is also well known that -in the receiving apparatus itis customary to provide a similar disc having a spiral series of holes or perforations therein interposed between the screen and a neon tube which is responsive to variations in the photoelectric cell of the transmitting apparatus. that it is absolutely necessary to have the scanning disc of the transmitting apparatus in perfect synchronism or timing with that of the receiving apparatus as otherwisethe light graduations or gradations or other fluctuations or variations would not be visible so that the entire apparatus would fail.

A more specific object of the invention is to provide in a television apparatus or system a scanning disc having an auxiliary perforation or hole therein provided for the sole purpose of,.coperating with the source of light and the photoelectric cell or neon tube,

as the case maybe, for the purpose of efiecting the synchronization of the motors which drive the scanningwdiscs' of the transmitting and receiving apparatus.

A vfurther object is to provide in a system of this character a synchronizing means which will be fixed and which may not necessarily be apart of or provided with the 'scannin disc. itself; but which may be formed as an a junct' for example in an auxiliary disc It is also known consequently the scanning disc will be exactly synchronized with the rotation of the scanning disc of the transmitter.

An additional object is to provide an apparatus of this character which willbe simple and inexpensive to make, assemble or install,

positive in action, efiicient and durable in service, and a eneral improvement in the art.

With the a ve and other objects and advantages in view, the invention preferably consists in the details of construction and the arrangement and combination of parts to be hereinafter more fully described and claimed,

and illustrated in the accompanying drawin 's, in which v igure 1 is a partial perspective and partial diagrammatic view illustrating the transmitting apparatus.

Figure 2 is a similar view of the receiving ap 'aratus.

igure 3 1s a detail view of the receiving a}: t e

paratus showing the relative location 0 tubes with respect to the auxiliary or syn chronizing apertured disc.

7 Referring more particularly to the drawings/Figure 1 illustratesdiagrammatically a television transmitting set or apparatus in which there is a source of light 10 adapted to project rays through'an aperture 11 in a screen 12, the rays falling onto and being adapted to pass through a spiral series of erforations 13in a scanning disc 14 mounts on a shaft 15 driven by an electric motor 16. At the opposite side of the disc there is a photoelectric cell 17 connected in arallel with a plurality of photoelectric cel s 18 which are connected in the transmittin system which includes the amplifiers 19 an '20, of conventional design, which are in turn connected with a transmitting antenna or aerial 21. In carrying out the invention I provide the scanning disc 14 with an additional hole 22 positioned between the screen 12 or rather the aperture 11 therein and the photoelectric cell 17 which is shielded by a shield 23 so that the light falling onto this, photoelectric cell 17 cannot in any way act upon the cells 18.

The receiving apparatus shown in Figure 2 comprises a scanning disc 24 having a spiral series of perforations 25 therein through which is adapted to be projected a ray of light from a neon tube 26, the light being thrown onto a screen 27 of the usual design. The disc 24 is represented as mounted upon a shaft 28 driven by an electric motor 29 connected with a source of current indicated by the leads 30. Interposed in one lead is a resistance 31 contacted by a movable arm 32 shown as pivoted and having an armature 33 operating between a pair of electromagnets 34 and 35 which constitute a relay device control, these magnets being connected with a suitable source of current 36 and with photo electric cells 37 located at opposite sides of a dividing screen 38.

The essential feature in the receiving apparatus is the provision of an auxiliary disc 39 mounted upon the shaft 28 or otherwise driven with the scanning disc 24-and provided with a single aperture 40, adapted to have a ray of light pass therethrough from a neon tube'41 connected in parallel with a tube 26 so as to operate simultaneously therewith. Clearly, if such is desired, the auxiliary disc 39 with its hole 40 might be omitted and the hole 40 be provided in the scanning disc 24, there being nothing of any great importance in this variation, the whole point being that there must be the auxiliary hole 40 interposed between the tubes 37 and the tube 41.

In the, operation, the time signal is received by the neon tubes 26 and 41. The first line across the screen 27 will show the time signal but this will not interfere with the balance of the lines and therefore will not in any way interfere with the picture itself. The neon tube 41 receives all the signals but as the small disc 39 has only one hole 40 therein this tube will show only the time signal through the hole/to the photoelectric cells 37. When the scanning disc 24 is turning in exact relation to the transmitting disc 14, or in proper synchronization therewith, the time signal Wlll fall evenly half and half on the photoelectric cells 37. However, should the motor 29 lag so that the disc would fail to reach the proper place of time signalthen the time signal will fall only on one cell 37, which cell is connected to the relay device, to increase the current to the motor by reducing the resistance by changing the pos tion of the arm 32 upon the coil 31. However, should the motor be too fast, the time signal will fall on the other cell 37 and increase the resistance so as to decrease the speed of the motor. This relay or resistance device is so arranged as to increase or decrease the speed of the motor in just the instantnecessary to effect roper synchronization of the motor and the i'sc.

From the foregoing description and a stud of the drawings'it will be apparent that have thus provided a very simple means whereby there will be attained a perfect synchronization of the scanning disc of the receiving apparatus with respect to the rotating disc of the transmitting apparatus. Using very sensitive relay means any small ditierencein the amount of light received by either of the two photoelectric cells 37 will effect the proper change in resistance in the motor circuit to synchronize everything perfectly. There is no question as to the length of time as this will be automatically compensated for at all times and for any length of time.

While I have shown and described thepreferred'embodiment of the invention, it should of course be understood that I reserve the right to make all such changes in the details of construction and the arrangement and" combination of parts aswill not depart from the spirit of the invention or the scope of the subjoined claims, as. for example I may Vfind it possible to provide the aperture 40 in the scanning disc 24 itself so as to eliminate the provision of the auxiliary disc 39. Furthermore other types of cells could be used instead of those specified without in any way departing from the invention.

Having thus described the invention, I claim i 1. In a television apparatus, a rotary receiving disc provided with a series of scanning holes, a second disc rotating with said first named disc, a motor for driving both of said discs, a screen, a neon lamp disposed at the side of the first named disc opposite the screen and adapted to receive current impulses, a second neon lamp connected in arallel with said first named neon lamp and arranged adjacent the second named disc, said second named disc having a finger holetherein for synchronizing purposes, a pair of photo-elcctric cells located adjacent the second named disc at the side opposite the second named neon lamp, a screen located between said pair of photo-electric cells, a resistance interposed in one of the leads to said motor, a movable arm'ada ted to travel over said resistance, and a pair of electro-magnetslocated at opposite sides of said arm and connected in parallel with a source of current and with the respective photo-electric cells for moving said arm in accordance with variations in the current to the electro-ma ets in response to fluctuations caused by the cam of light passing from the second named neon lamp through said hole onto one o1 the other of said photo-electric cells.

2. In a television apparatus, receivingmeans includinga rotary disc having a synchronizing hole therein a neon lamp arranged at one side of said disc for projecting a. beam of light through said hole, said neon v lamp being responsive to fluctuations of ourrent generated at a transmitting station, a pair of photo-electric cells located at the oposite sides of said disc and having a screen interposed between them, a motor for driving said disc, and means responsive to the assa e of light throu h said holefor control ing t e speed of sai motor comprising a. pair of electro-magnets connected 1n common with a said con; 7 

